The Case of the 12 May 2010 Event in North Korea: the Role of Temporary Seismic Deployments as National Technical Means for CTBT Verification

Abstract:

Since 2012 there has been debate about a low-yield nuclear explosion within North Korea, initially claimed to have occurred in April/May 2010 on the basis of a number of Level 5 radionuclide detections from stations of the radionuclide subnetwork of the International Monitoring System (IMS) and additional reports from similar national facilities. Whereas the announced nuclear tests in North Korea in 2006, 2009 and 2013, were clearly detected seismically, there was initially a lack of detections from the seismological component of the IMS corresponding to a possible nuclear test in 2010.

Work published recently by Zhang and Wen in Seismological Research Letters (Jan/Feb 2015) inferring seismological evidence for an explosion in North Korea, at about 0009 hours on 12 May 2010 (UTC), has attracted further attention. Previous studies of seismicity of the North Korean test site for days prior to this date had not found any such evidence from IMS or non-IMS stations. The data used by Zhang and Wen were from stations in northeastern China about 80 to 200 km from the North Korean test site and are currently not available for open research. A search for openly-available data was undertaken, resulting in relevant waveforms obtained both from the IRIS Consortium (from a PASSCAL experiment in Northeastern China, as noted also by Ford and Walter, 2015), and from another temporary seismic deployment, also in China. The data from these stations showed signals consistent with the seismic disturbance found by Zhang and Wen. These supplementary stations thus constitute a monitoring resource providing objective data, in the present case for an event even below magnitude 2 and thus much smaller than can be monitored by the usual assets. Efforts are currently underway to use the data from these stations to investigate the compatibility of the event with other explosion-type events, or with an earthquake.